Effect of dietary fat saturation and cholesterol on LDL composition and metabolism. In vivo studies of receptor and nonreceptor-mediated catabolism of LDL in cebus monkeys.
The mechanism(s) by which polyunsaturated fats reduce low density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B were investigated in 20 cebus monkeys (Cebus albifrons) fed diets containing corn oil or coconut oil as fat (31% of calories) with or without dietary cholesterol (0.1% by weight) for 3 to 10 years. Coconut-oil feeding compared to corn-oil feeding resulted in significant increases in levels of plasma total cholesterol (176%), very low density lipoprotein (VLDL)-LDL cholesterol (236%), high density lipoprotein (HDL) cholesterol (148%), apo B (78%), and apo A-I (112%). The addition of dietary cholesterol to corn oil compared to corn oil alone resulted in smaller, but significant, increases in levels of total cholesterol (44%), HDL cholesterol (40%), and apo A-I (33%). Although the increases in VLDL-LDL cholesterol were of similar magnitude (52%), they barely failed to reach statistical significance (p less than 0.08), while the changes in apo B levels were negligible. The addition of dietary cholesterol to coconut oil, compared to coconut oil alone, resulted in no significant changes in lipoprotein cholesterol or apoproteins, although levels of VLDL-LDL cholesterol and apo B values increased 22% and 16%, respectively. Although hepatic free cholesterol content was not altered by diet, coconut-oil compared to corn-oil feeding resulted in significant increases in hepatic cholesteryl esters (236%) and triglycerides (325%), the latter increasing still further when dietary cholesterol was added to coconut oil (563%). To further assess the effects of these dietary changes on LDL metabolism, radioiodinated normal and glucosylated LDL kinetics were performed. The production rate of LDL apo B was not altered by diet. With corn-oil feeding, 63% of LDL catabolism was via the receptor-mediated pathway. Coconut-oil compared to corn-oil feeding resulted in a 50% decrease in receptor-mediated LDL apo B fractional catabolic rate (FCR) and a 27% reduction in nonreceptor-mediated LDL apo B FCR. The addition of dietary cholesterol to corn oil, compared to corn oil alone, resulted in no significant effect on LDL apo B catabolism. The addition of dietary cholesterol to coconut oil, compared to coconut oil alone, was associated with no significant change in nonreceptor catabolism of LDL apo B but with a 58% decrease in receptor-mediated catabolism of LDL (p less than 0.059). The diet-induced alterations of LDL catabolism were significantly correlated with hepatic lipids, which were enriched in saturated fatty acids.(ABSTRACT TRUNCATED AT 400 WORDS)
Nicolosi
R J
RJ
Department of Clinical Sciences, University of Lowell, Massachusetts 01854.
Stucchi
A F
AF
Kowala
M C
MC
Hennessy
L K
LK
Hegsted
D M
DM
Schaefer
E J
EJ
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001055:Apolipoproteins B / Q000378:metabolism; D002428:Cebus; D002788:Cholesterol Esters / Q000378:metabolism; D002791:Cholesterol, Dietary / Q000378:metabolism*; D000074263:Coconut Oil; D003314:Corn Oil / Q000378:metabolism; D004041:Dietary Fats / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D010938:Plant Oils; D011973:Receptors, LDL / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
D001055:Apolipoproteins B; D002788:Cholesterol Esters; D002791:Cholesterol, Dietary; D004041:Dietary Fats; D008077:Lipoproteins, LDL; D010743:Phospholipids; D010938:Plant Oils; D011973:Receptors, LDL; D014280:Triglycerides; D003314:Corn Oil; D000074263:Coconut Oil